This invention relates to an improved process for hydroconverting carbonaceous materials to lower molecular weight products. More particularly, this invention relates to an improved catalytic process for hydroconverting carbonaceous materials to lower molecular weight products.
Heretofore, several catalytic processes for hydroconverting solid carbonaceous materials such as coal, lignite, peat and the like to lower molecular weight products and for converting heavier petroleum fractions such as atmospheric and vacuum residuals to lower molecular weight products have been proposed. The lower molecular weight products may be gaseous or liquid or a mixture of both. In general, the production of liquid products is particularly desirable since liquid products are more readily stored and transported and the lower molecular weight liquid products are often conveniently used as motor fuels.
Heretofore, a large number of suitable catalysts have been identified as useful in such hydroconversion processes. For example, transition metal sulfides and oxides and mixtures thereof have been particularly useful as catalysts in such processes. Moreover, a host of catalyst precursors; that is, compounds that will either decompose or are readily converted to an active sulfide or oxide form, have been identified. Such precursors include transition metal complexes such as transition metal naphthenates and heteropoly metal acids and inorganic compounds such as ammonium salts of transition metals. In general, the precursors used have either been soluble, to some extent, in the reaction medium itself or in a solvent which is either added to the reaction medium or used to facilitate impregnation. The solvents heretofore employed have been both organic and inorganic.
As is well known in the prior art, the effectiveness of the transition metal sulfide and oxide catalyst precursors has been limited by their respective solubilities at atmospheric conditions or upon heating in the reaction media itself or in the solvent used to incorporate the same into the reaction media. While the reason or reasons for this limitation on catalytic activity is not well known, it is believed to be due either to the particle size of the active catalyst species ultimately formed in the reaction media or as a result of poor distribution of the active catalyst species within the reaction mixture. Moreover, most, if not all, of the precursor species proposed heretofore require a treatment of some kind with a sulfur compound before the more active sulfide catalyst species is ultimately obtained. Since the catalytic processes heretofore proposed have experienced effectiveness limitations due either to the formation of relatively large particle size catalyst species or as a result of poor distribution of the catalyst species within the reaction media and since most, if not all, require some treatment with a sulfur compound, the need for an improved catalytic process wherein the catalytic activity is improved either as a result of reduced particle size or improved distribution and wherein a special treatment with a sulfur compound is not required is believed to be readily apparent.